Photothermographic element

ABSTRACT

A SENSITIZING DYE WHICHH IS A MEROCYANINE DYE CONTAINING A RHODANINE, THIOHYDANTOIN OR 2-THIO-2,4-OXAZOLIDINEDIONE NUCLEUS IN COMBINATION WITH AN IMAGE-FORMING COMNBINATION COMPRISING (A) A REDUCING AGENT, SUCH AS A PHENOLIC REDUCING AGENT, AND (B) AN OXIDIZING AGENT, SUCH AS A HEAVY METAL SALT OF AN ORGANIC CARBOXYLIC ACID, WITH (C) A CATALYST FOR THE DESCRIBED IMAGE-FORMING COMBINATION, E.G., PHOTOSENSITIVE SILVER HALIDE AND PREFERERABLY WITH (D) AN ACTIVATOR- TONING AGENT, SUCH AS A CYCLIC IMIDE, IN A PHOTOSENSITIVE AND THERMOSENSITIVE COMPOSITION OR ELEMENT, PROVIDES INCREASED PHOTOSENSITIVITY, ESPECIALLY IN THE BLUE REGION OF THE SPECTRUM, FASTER DEVELOPMENT, HIGHER MAXIMUM DENSITY, A MORE NEUTURAL TONE AND LESS BACKGROUND DENSITY DUE TO POST-PROCESSING PRINTOUT. THE DESCRIBED COMBINATION CAN ALSO CONTAIN A DIVALENT METAL SALT IMAGE AMPLIFIER, SUCH AS ZINC ACETATE, AN IMAGE STABILIZER PRECURSOR, SUCH AS AN AZOLE THIOETHER STABILIZER PRECURSOR, AND A PHOTOGRAPHIC SPEED INCREASING, ONIUM PRECURSOR, AND A PHOTOGRAPHIC SPEED INCREASING,ONIUM HALIDE.

United States Patent US. Cl. 96114.1 5 Claims ABSTRACT OF THE DISCLOSURE A sensitizing dye which is a merocyanine dye containing a rhodanine, thiohydantoin or 2-thio-2,4-oxazolidinedione nucleus, in combination with an image-forming combination comprising (a) a reducing agent, such as a phenolic reducing agent, and (b) an oxidizing agent, such as a heavy metal salt of an organic carboxylic acid, with (c) a catalyst for the described image-forming combination, e.g., photosensitive silver halide and prefererably with (d) an activator-toning agent, such as a cyclic imide, in a photosensitive and thermosensitive composition or element, provides increased photosensitivity, especially in the blue region of the spectrum, faster development, higher maximum density, a more neutral tone and less background density due to post-processing printout. The described combination can also contain a divalent metal salt image amplifier, such as zinc acetate, an image stabilizer precursor, such as an azole thioether stabilizer precursor or a blocked azole thione stabilizer precursor, and a photographic speed increasing, onium halide.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to photosensitive elements, compositions and processes for developing a latent image using so-called dry processing with heat. In one of its aspects, it relates to a photosensitive element suitable for dry processing with heat containing an image-forming combination comprising (a) a reducing agent, especially a phenolic reducing agent, such as a bis-naphthol reducing agent, and (b) an oxidizing agent, especially a heavy metal salt of an organic carboxylic acid, e.g., silver behenate and a sensitizing dye which has the properties of increasing the blue sensitivity of the element, especially a merocyanine dye containing a rhodanine, thiohydantoin, or 2-thio-2,4-oxazolidinedione nucleus. In another of its aspects, it relates to a photosensitive composition suitable for dry processing with heat containing an image-forming combination comprising (a) a reducing agent, especially a phenolic reducing agent, such as a bis-naphthol reducing agent, (b) an oxidizing agent, as described, and a sensitizing dye which has the property of enhancing the blue sensitivity of the element, as described. A further aspect relates to a process of developing a latent image in a photosensitive and thermosensitive composition or element, as described, containing a merocyanine dye also as described.

Description of the state of the art A number of methods have been described previously for increasing the sensitivity of photographic silver halide emulsions. It is known that the sensitivity of photographic emulsions can be increased by chemical sensitization. Chemical sensitization is carried out by the addition to a silver halide emulsion of sulfur compounds capable of reacting with silver salts to form silver sulfide, or with reducing agents, or with salts of gold or other noble metals, or with combinations of two or more of these compounds. The process of chemical sensitization reaches a definite limit beyond which further addition of chemical sensitizer, or of further digestion with the sensitizer present, merely increases the fog of the photographic emulsion with constant or decreasing speed.

It is also known in the art of making photographic elements that certain dyes of the cyanine class, e.g., merocyanines, cyanines, hemicyanines, and the like, alter the sensitivity of photographic silver halide emulsions when the dyes are incorporated in the emulsions. The spectral sensitization provided by a given dye may vary somewhat with the type of emulsion in which the dye is incorporated. But, a spectral sensitizer usually does not increase the sensitivity of a grain throughout the Whole spectrum. Also, a dye is usually both a sensitizer and a desensitizer depending upon concentration of the dye and other factors. Thus, an optimum concentration of dye is usually determined for an emulsion which has already been optimally chemically sensitized. Very few dyes are free from desensitizing characteristics.

It is further known to obtain an image in a photosensitive and thermosensitive element, suitable for socalled dry processing with heat. The photosensitive element can contain an oxidation-reduction image-forming combination containing (a) a reducing agent, (b) an oxidizing agent, e.g. a light insensitive silver salt of an organic acid and (c) a catalyst for the image-forming combination which is usually a low concentration of photographic silver halide. These are described, for example, in US. Pat. 3,152,904 of Sorensen and Shepard, issued Oct. 13, 1964, US. Pat. 3,457,075 of Morgan and Shely, issued July 22, 1969, British Pat. 1,161,777 published Aug. 20, 1969, and British Pat. 1,163,187, published Sept. 4, 1969.

It is also known that spectral sensitizing dyes can be employed in photosensitive and thermosensitive elements to increase spectral sensitivity. This is described, for example, in US. Pat. 3,457,075 of Morgan and Shely, issued July 22, 1969, British 1,161,777 and British Pat. 1,163,- 187. Spectral sensitizing dyes, however, provide no increase or even reduce sensitivity in the blue region of the spectrum, in many cases in these elements, as demonstrated in following comparative Examples ll, 12 and 14.

Photosensitive elements for processing with heat have in many cases lacked desired sensitivity in the blue region of the spectrum and the images after processing have been of low maximum density, undesired warm tone and have undesirably high background density.

Accordingly, there has been a continuing need for photosensitive and thermosensitive elements which have increased photosensitivity, especially in the blue region of the spectrum, provide faster development, higher maximum density, a more neutral (black) tone and less background density due to post-processing print-out.

SUMMARY OF THE INVENTION The desired improvements, according to the invention, are provided in a photosensitive and thermosensitive, also referred to herein as photothermographic element, composition and process for developing a latent image in such an element or composition, employing (a) an oxidation-reduction image-forming combination comprising 1) a reducing agent with (2) an oxidizing agent which comprises a heavy metal salt of an organic carboxylic acid, ('b) a catalyst for said image-fouming combination, and (c) a sensitizing dye comprising a merocyanine sensitizing dye having a rhodanine, thiohydantoin or 2- thio-2,4-oxazolidinedione nucleus.

These sensitizing dyes provide a surprising increase in sensitivity in the blue region of the spectrum in such elements, compositions and processes, as described.

DETAILED DESCRIPTION OF THE INVENTION A number of sensitizing dyes can be employed in the practice of the invention to enhance the blue sensitivity of a photosensitive and thermosensitive element, e.g., enhance sensitivity in the range of wavelengths of about 320 to about 500 millimicrons. These dyes, in addition to increasing the inherent blue sensitivity of the element, cause spectral sensitization also. These sensitizing dyes can be employed, if desired, in combination with other spectral sensitizing dyes.

The sensitizing dye which is described herein as a blue speed-increasing sensitizing dye and which is preferred is a merocyanine dye of the following general formula:

wherein R is alkyl of the formula CnH n+l, preferably methyl, ethyl, propyl or butyl; n represents a positive integer of from 1 to 4; R is hydrogen or alkyl of the formula CaH a+1 wherein a represents a positive integer of from 1 to 2, preferably methyl or ethyl; Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus which is a nucleus of the benzothiazole, thiazoline, or benzoxazole series, and Q represents the nonmetallic atoms, necessary to complete a rhodanine, thiohydantoin, or 2-thio-2,4-oxazolidinedione nucleus, preferably containing in the three position an alkyl group containing 1 to 3 carbon atoms, i.e., methyl, ethyl or propyl, a carboxyalkyl group containing 1 to 3 carbon atoms in addition to the carboxyl group carbon atom, e.g., carboxymethyl, carboxyethyl or carboxypropyl, amino alkyl such as pyrrolinyl propyl, or aryl, e.g., aryl containing 6 to 12 carbon atoms such as phenyl, xylyl, tolyl. The aryl group can contain substituents which do not adversely affect the desired properties of the dye, e.g., the property of causing an increase in speed in the blue region of the spectrum, such as a carboxy group.

A preferred merocyanine dye is 3-carboxymethyl-5-[(3- methyl 2[3H] thiazolinylidene)isopropylidene]rhodanine of the formula:

TN-CHzCOzH Other examples of suitable merocyanine dyes which can be employed in the practice of the invention include:

( 1) 3-p-carboxyphenyl-5- [,B-ethyl-Z (3 -benzoxazolyidene)ethylidene]rhodanine,

(2) 3-B-carboxyethyl-2 3-thiazolinylidene) ethylidene]-3-ethylrhodanine,

(3) 3-carboxymethyl-5- 3-methylthiazolinylidene)-aethylethylidene]-rhodanine,

(4) 1-carboxymethyl-5-[ (3-ethyl-2- 3H -benzoxazolylidene ethylidene] -3-phenyl-2-thiohydantoin,

(5 5- (3-ethyl-2-benzoxazolinylidene)-l-methylethylidene] -3- [3-pyrro1inl-yl -propyl] rhodanine, and/ or (6) 3-ethyl-5-[(3-ethyl-2(3H)-benzothiazolylidene)isopropylidene] -2-thio-2,4-oxazolidinedione.

The described merocyanine dyes are suitable in a wide range of concentration in the described compositions and elements. A typical concentration is about 50 mg. to

about 2.0 grams of the described dye per mole of described catalyst, e.g., photosensitive silver halide; however, the dye is suitable, at a concentration from about 400 mg. to about 1.0 gram per mole of photosensitive silver halide, according to the invention in an element or composition as described.

It is believed that the described dyes enhance the sensitivity of the catalyst, i.e., photosensitive silver halide present in the photosensitive element or com osition through an oxidation-reduction mechanism, thereby enhancing the photosensitive response of the element or composition in the intrinsic blue region of silver halide which is not related to any spectral sensitivity which may be conferred on the element due to the absorption of light by the dyes in those regions not normal to photographic silver halide. The exact mechanism of how the described dyes enhance speed in the blue region of the spectrum is not fully understood. Regardless of the mechanism involved, it is demonstrated that certain merocyanine dyes increase the blue sensitivity of the photosensitive and thermosensitive element or composition according to the invention as described and, in addition, provide an unexpected increase in the rate of development as set out in following Example 16.

One embodiment of the invention is a photosensitive and thermosensitive element comprising a support, (a) an oxidation-reduction image-forming combination comprising (l) a reducing agent with (2) an oxidizing agent which comprises a heavy metal salt of an organic carboxylic acid, (b) a catalyst for said image-forming combination, and (c) a sensitizing dye comprising a merocyanine sensitizing dye having a rhodanine, thiohydantoin or 2-thio-2,4-oxazolidenedione nucleus.

Another embodiment of the invention is a photosensitive and thermosensitive composition comprising (a) the described oxidation-reduction image-forming combination, (b) a catalyst for said image-forming combination, as described, and (c) a sensitizing dye, also as described.

The described element or composition contains a catalyst for the image-forming combination, especially a photosensitive silver salt. A typical concentration range of photo-sensitive silver salt is from about 0.005 to about 0.50 mole of silver salt per mole of oxidizing agent such as per mole of silver salt of organic acid, e.g., per mole of silver behenate. A preferred catalyst is photosensitive silver halide, e.g., silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide, or mixtures thereof. The photosensensitive silver halide can be coarse or fine-grain, very fine-grain emulsions being especially useful. The emulsion containing the photosensitive silver halide can be prepared by any of the well-known procedures in the photographic art, such as single-jet emulsions, double-jet emulsions, such as Lippman emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions, such as those described in U.S. Pat. 2,222,264 of Nietz et al., issued Nov. 14, 1940; U.S. Pat. 3,320,069 of Illingsworth, issued May 15, 1967, and U.S. Pat. 3,271,- 157 of McBride, issued Sept. 6, 1966. Surface image silver halide emulsions can be used if desired mixtures of surface and internal image silver halide emulsions can be used as described in U.S. Pat. 2,996,332 of Luckey et al., issued Apr. 15, 1961. Negative type emulsions can be used. The silver halide emulsion can be a regular grain emulsion such as described in Klein and Moisar, Journal of Photographic Science, vol. 12, No. 5, September-October (1964), pp. 242-251.

The silver halide emulsions employed in the practice of the invention can be unwashed or Washed to remove soluble salts. In the latter case the soluble salts can be removed by chill setting and leaching or the emulsion can be coagulation washed.

The silver halide employed in the practice of the invention can be sensitized with chemical sensitizers, such as with reducing agents; sulfur, selenium, or tellurium compounds; gold, platinum, or palladium compounds, or combinations of these. Suitable procedures are described for example, in U.S. Pat. 1,623,499 of Shepard, issued Apr. 5, 1927; U.S. Pat. 2,399,083 of Waller et al., issued Apr. 23, 1946; U.S. Pat. 3,297,447 of McVeigh, issued Jan. 10, 1967; and U.S. Pat. 3,297,446 of Dunn, issued Jan. 10, 1967.

Photosensitive silver halide emulsion employed in the practice of the invention can be protected against the production of fog and can be stabilized against loss of sensitivity during keeping. Suitable antifoggants and stabilizers, e.g., used alone or in combination include, for example, thiazolium salts; azaindenes; mercury salts as described, for example in US. Pat. 2,728,663 of Allen et a1. issued Dec. 27, 1955, urazoles; sulfocatechols; oximes described, for example, in British Pat. 623,448; nitron; nitroindazoles; polyvalent metal salts described, for example, in US. Pat. 2,839,405 of Jones issued June 17, 1958; platinum, palladium and gold salts described, for example, in US. Pat. 2,566,263 of Trivelli et a1. issued Aug. 28, 1951 and US. Pat. 2,597,915 of Yutzy et al. issued May 27, 1952.

Suitable organic reducing agents which can be employed in the described combination include, for example, substituted phenols and naphthols. The bis-naphthols which is preferred is a bis-fl-naphthol of the formula:

2,2'-dihydroxy- 1, 1 '-binaphthyl, 6,6'-dibrorno-2,2-dihydroxy-1,1'-binaphthyl, 6,6-dinitro-2,2-dihydroxy-1,1'-binaphthyl, and/or Bis-(2-hydroxy-1-naphthyl)methane.

The described reducing agents are suitable in a range of concentration; however, they are especially suitable, at a concentration from about 0.10 to about 0.75 mole of reducing agent per mole of oxidizing agent, e.g., per mole of silver behenate.

Reducing agents which are typically silver halide developing agents can be used in conjunction with or in place of the above bis-naphthol reducing agents. Suitable silver halide developing agents include for example, polyhydroxybenzenes such as hydroquinone developing agents, e.g., hydroquinone, alkyl-substituted hydroquinones as exemplified by tertiary butylhydroquinone, methylhydroquinone, 2,5-dimethylhydroquinone and 2,6-dimethylhydroquinone; catechols and pyrogallol; halo-substituted hydroquinones such as chlorohydroquinone, or dichlorohydroquinone; alkoxy-substituted hydroquinones such as methoxyhydroquinone or ethoxyhydroquinone; methylhydroxynaphthalene; phenylenediamine developing agents; methylgallate; aminophenol developing agents, such as 2, 4-diaminophenols and methylaminophenols; ascorbic acid developing agents such as ascorbic acid, ascorbic acid ketols and ascorbic acid derivatives such as those described in US. Pat. 3,337,342 of Green issued Aug. 22, 1967; hydroxylamine developing agents such as N,N-di- (Zethoxyethyl)hydroxylamine; 3 pyrazolidone developing agents such as l-phenyl-3-pyrazolidone and 4-methyl 4 hydroxymethyl-l-phenyl-3-pyrazolidone including those described in British Pat. 930,572 published July 3, 1963; hydroxytetronic acid, and hydroxytetronamide developing agents, reductone developing agents such as anhydrodihydropyrrolidino hexose reductone; and the like.

The described elements comprise an oxidizing agent, especially a heavy metal salt of an organic acid. The heavy metal salts of the organic acids should be resistant to darkening under illumination to prevent undesired deterioration of a developed image. An especially suitable class of heavy metal salts of organic acids is represented by the water insoluble silver salts of long-chain fatty acids which are stable to light. Compounds which are suitable silver salts include silver behenate, silver stearate, silver 6 oleate, silver laurate, silver hydroxystearate, silver caprate, silver myristate and silver palmitate.

Other suitable carboxylic acid silver salt oxidizing agents, which are not silver salts of long-chain fatty acids include silver benzoate, silver 4-n-octadecyloxydiphenyl- 4-carboxylate, silver o-aminobenzoate, silver acetamidobenzoate, silver furoate, silver camphorate, silver p-phenylbenzoate, silver phenylacetate, silver salicylate, silver butyrate, silver terephthalate, silver phthalate, silver acetate and silver acid phthalate.

Oxidizing agents which are not silver salts of a car boxylic acid can be employed, if desired, such as silver phthalazinone, silver benzotriazole and silver saccharin. Oxidizing agents which are not silver salts can be employed, if desired, such as zinc oxide, gold stearate, mercuric behenate, auric behenate and the like, but silver salts are preferred.

It is desirable to employ an activator-toning agent in the elements, compositions and processes of the invention to obtain a desired image particularly when phenolic reducing agents are used. A suitable activator-toning agent is a heterocyclic activator-toning agent containing at least one nitrogen atom and of the formula:

where R is hydrogen, hydroxyl, or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; Z, represents atoms completing a heterocyclic nucleus, especially a 5 to 6 member heterocyclic nucleus. The atoms completing the heterocyclic nucleus can be, for example,

or an alkylene group containing 3 to 4 carbon atoms. The atoms completing the heterocyclic nucleus can contain various substituent groups, such as amino, alkyl amino, e.g., methylamino or ethylamino, hydroxyl, carbamyl and the like. An especially suitable activator-toning agent is a heterocyclic activator-toning agent containing at least one nitrogen atom which is preferably a cyclic imide of the formula:

wherein R can be hydrogen, hydroxyl, or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; Z represents carbon atoms of a series completing a cyclic imide nucleus, typically consisting of from '5 to 6 carbon atoms, e.g., a phthalimide or succinimide nucleus. The atoms of the cyclic imide nucleus can contain various substituent groups, especially amino, alkyl, such as alkyl containing 1 to 5 carbon atoms, such as methyl, ethyl, propyl, butyl, or pentyl or aryl, such as aryl containing 6 to 20 carbon atoms, such as phenyl, tolyl and xylyl. Suitable activator-toning agents which can be employed in the practice of the invention include:

Phthalimide, N-hydroxyphthalirnide, N-potassium phthalimide, N-silver phthalimide, N-mercury phthalimide, succinimide, and/or N-hydroxysuccinimide.

The described activator-toning agents are suitable in a range of concentration; however, they are especially suitable at a concentration of about 0.10 mole to about 1.05 moles of activator-toning agent per mole of oxidizing agent, e.g., per mole of silver behenate.

Other so-called activator-toning agents can be employed in combination with or in place of the described cyclic imide activator-toning agents. Typically a heterocyclic organic toning agent containing at least two hetero atoms in the heterocyclic ring of which at least one is a nitrogen atom is employed. These are described, for example, in U.S. Pat. 3,080,254 of Grant issued Mar. 5, 1963. Suitable toners include, for example, phthalazinone, phthalic anhydride, 2-acetylphthalazinone and Z-phthalylphthalazinone. Other suitable toners are described, for example, in U.S. Pat. 3,446,648 of Workman issued May 27, 1969.

A non-aqueous, polar, organic solvent such as a compound containing a ll ll 0 moiety, in a described photosensitive and thermosensitive element or composition suitable for dry processing with heat can in many cases provide improved maximum image densities. Suitable non-aqueous solvents include, for example, tetrahydrothiophene-1,1-dioxide, 4-hydroxybutanoic acid lactone and methylsulfinylmethane.

A divalent metal salt which has the property of amplifying the developed image can be employed in the practice of the invention to cause an increase in maximum image density. A suitable divalent metal salt image amplifier is zinc acetate, cadmium acetate or cupric acetate. The described image-amplifying compounds are suitable in a range of concentration of about 0.005 to about 0.20 mole of divalent metal salt image amplifier per mole of silver salt oxidizing agent; however, they are especially suitable at a concentration from about 0.010 mole to about 0.10 mole of divalent metal salt image amplifier per mole of silver salt oxidizing agent according to the invention in an element as described.

It is desirable to employ an image stabilizer precursor in the described elements or compositions of the invention. These can be employed in the practice of the invention to reduce the amount of post-processing print-out due to room light exposure and to reduce the background stain. Suitable stabilizer precursors include azole thioethers and blocked azole thione stabilizer precursors, e.g., S-acetyl 4 methyl-2-(3-oxobutylthio)thiazole, 4-furoyl- 3-methylthio-l,2,4-thiadiazole-5 thione, 5-acetyl-4-methyl-3-(3-oxobutyl)thiazoline-Z-thione and 2,6-di-tert-butyl- 4-(l-phenyl-S-tetrazolyl)thiophenol. The described stabilizer precursors are suitable in a range of concentration; however, they are especially suitable at a concentration from about 0.002 mole to about 0.10 mole of stabilizer precursor per mole of oxidizing agent, e.g., per mole of silver behenate in an element or composition as described.

A range of colorless onium halides can be employed in the described elements or compositions to provide an additional increase in photosensitivity, i.e., speed, and in some cases to obtain a reduction in background density. A suitable speed-increasing onium halide compound is a quaternary ammonium halide, quaternary phosphonium halide and/or a tertiary sulfonium halide, e.g., l-phenethyl-Z-picolinium bromide, tetraethylphosphonium bromide or trimethylsulfonium iodide. An optimum concentration can be determined for each onium halide. A suitable test to determine the optimum concentration of onium halide is set out in following Example 19. An onium halide is added at various concentrations to a final coating dispersion as described in this example. The dispersion is then coated on a suitable support and compared to an element which does not contain an onium halide compound. If after exposure and heat processing the test element does not show a relative speed increase of or more units, then the concentration of onium halide is not considered as satisfactory. An especially suitable onium halide is trimethylphenylammonium bromide which is typically employed at a concentration of about 0.010 mole to about 0.05 mole per mole of catalyst, e.g., per mole of photosensitive silver halide.

A photosensitive and thermosensitive element and compositions described and used in the practice of the invention can contain various colloids alone or in combination as vehicles, binding agents and in various layers. Suitable materials are typically hydrophobic but hydrophilic materials can also be employed. They are transparent or translucent and include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water-soluble polyvinyl compounds like poly(vinyl pyrrolidone), acrylamide polymers and the like. Other synthetic polymeric compounds which can be employed include dispersed vinyl compounds such as in latex form and particularly those which increase dimensional stability of photographic materials. Suitable synthetic polymers include those described in U.S. Pat. 3,142,586 of Nottorf issued July 28, 1964; U.S. Pat. 3,193,386 of White issued July 6, 1955; U.S. Pat. 3,062,674 of Houck et al. issued Nov. 6, 1962; U.S. Pat. 3,220,844 of Houck et al. issued Nov. 30, 1965; U.S. Pat. 3,287,289 of Ream et al. issued Nov. 22, 1966; and U.S. Pat. 3,411,911 of Dykstra issued Nov. 19, 1968. Effective polymers include water insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, and those which have cross-linking sites which facilitate hardening or curing as well as those having recurring sulfobetaine units as described in Canadian Pat. 774,054. Preferred high molecular weight materials and resins include polyvinyl butyral, cellulose acetate butyrate, polymethyl methacrylate, poly(vinyl pyrrolidone), ethyl cellulose, polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene, butadiene-styrene copolymers, vinyl chloride-vinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid and polyvinyl alcohol.

The photosensitive and thermosensitive layers and other layers of an element employed in the practice of the invention and described herein can be coated on a wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly(vinylacetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film and related films or resinous materials, as well as glass, paper, metal and the like. Typically a flexible support is employed, especially a paper support which can be partially acetylated or coated with baryta and/or an alpha olefin polymer, particularly a polymer of an alpha olefin containing 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylenebutene copolymers and the like.

The photosensitive and thermosensitive and other hardenable layers of an element used in the practice of this invention can be hardened by various organic or inorganic hardeners, alone or in combination, such as aldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixed-function hardeners and polymeric hardeners such as oxidized polysaccharides like dialdehyde starch and oxyguargum and the like.

The photosensitive and thermosensitive elements used in the practice of the invention can contain antistatic or conducting layers. Such layers can comprise soluble salts such as chlorides, nitrates and the like, evaporated metal layers, ionic polymers such as those described in U.S. Pat. 2,861,056 of Minsk issued Nov. 18, 1958 and U.S. Pat. 3,206,312 of Sterman et al. issued Sept. 14, 1965 or insoluble inorganic salts such as those described in U.S. Pat. 3,428,451 of Trevoy issued Feb. 18, 1969. The photosensitive and thermosensitive elements can also contain antihalation materials and antihalation dyes.

The photosensitive and thermosensitive layers or other layers employed in the practice of the invention can contain plasticizers and lubricants. Suitable plasticizers and lubricants include, for example, polyalcohols such as glycerin and diols described, for example, in U.S. Pat. 2,960,404 of Milton et al. issued Nov. 1, 1966; fatty acids or esters such as those described in U.S. Pat. 2,588,765 of Robijns issued Mar. 11, 1952; U.S. Pat. 3,121,060 of Duane issued Feb. 11, 1964; and silicone resins such as those described in British 955,061.

The photosensitive and thermosensitive layers or other layers employed in the practice of the invention can contain surfactants such as saponin; anionic compounds such as alkylaryl sulfonates described, for example, in U.S. Pat. 2,600,831 of Baldsiefen issued June 17, 1962; amphoteric compounds such as those described in U.S. Pat. 3,133,816 of Ben-Ezra issued May 19, 1964; and adducts of glycidol and an alkyl phenol such as those described in British Pat. 1,022,878.

If desired, the photosensitive and thermosensitive elements employed in the practice of the invention can contain matting agents such as starch, titanium dioxide, zinc oxide, silica, polymeric beads including beads described, for example, in U.S. Pat. 2,922,101 of Jelley et al. issued July 11, 1961 and U.S. Pat. 2,761,245 of Lynn issued Feb. 1, 1955.

The photosensitive and thermosensitive elements and compositions employed in the practice of the invention can contain brightening agents including stilbenes, triazines, oxazoles, and coumarin brightening agents. Watersoluble brightening agents can be used such as those described in German Pat. 972,067 and U.S. Pat. 2,933,390 of McFall et al. issued Apr. 19, 1960 or dispersions of brighteners can be used such as those described in German Pat. 1,150,274; U.S. Pat. 3,406,070 of Oetiker et al. issued Oct. 15, 1968 and French Pat. 1,530,244.

The various layers including the photosensitive and thermosensitive layers of an element employed in the practice of the invention can contain light-absorbing materials, filter dyes, antihalation dyes and absorbing dyes such as those described in U.S. Pat. 3,253,921 of Sawdey issued May 31, 1966; U.S. Pat. 2,274,782 of Gaspar issued Mar. 3, 1942; U.S. Pat. 2,527,583 of Silberstein et al. issued Oct. 31, 1950; and U.S. Pat. 2,956,879 of Van Campen issued Oct. 18, 1960. If desired, the dyes can be mordanted, for example, as described in U.S. Pat. 3,282,699 of Jones et al. issued Nov. 1, 1966.

The photosensitive and thermosensitive layers used in the practice of the invention can be coated by various coating procedures including dip coating, airknife coating, curtain coating or extrusion coating using hoppers such as described in U.S. Pat. 2,681,294 of Beguin issued June 15, 1954. If desired, two or more layers can be coated simultaneously such as by the procedures described in U.S. Pat. 2,761,791 of Russell issued Sept. 4, 1956 and British Pat. 837,095.

If desired, the photosensitive silver halide can be prepared in situ, in the photosensitive and thermosensitive coatings of an element employed in the practice of the invention. Such a method is described, for example, in U.S. Pat. 3,457,075 of Morgan et al. issued July 22, 1969. For example, a dilute solution of a halogen acid such as hydrochloric acid, can be applied to the surface of a thin coating containing an organic silver salt, such as silver behenate, on a suitable substrate followed by removal of the solvent if desired. Silver halide is thus formed in situ throughout the surface of the coating of the organic silver salt.

The photosensitive silver halide can be prepared on the oxidizing agent, such as silver behenate or silver stearate, or other organic silver salt, prior to application of the silver halide on the support employed. This is also described in U.S. Pat. 3,457,075 of Morgan et al. issued July 22, 1969, for example, a halogen acid such as hydro- 10 chloric acid or hydrobromic acid can be mixed with an organic silver salt in a suitable reaction medium. A halide salt more soluble than the organic silver salt can be added to a suspension of the organic silver salt to form the silver halide. A suitable reaction medium includes water or other solvents which do not interfere with the reaction.

Stability to print out from light exposure is increased by employing highly purified materials; for example, freedom from halides and sulfides increase stability to light exposure. The use of highly purified silver behenate can, for example, reduce propensity to print out in background areas of an element prepared according to the invention.

Spectral sensitizing dyes can be used conveniently to confer additional sensitivity to the elements and compositions of the invention. For instance, additional spectral sensitization can be obtained by treating the silver halide with a solution of a sensitizing dye in an organic solvent or the dye can be added in the form of a dispersion as described in British Pat. 1,154,781. For optimum results the dye can either be added to the emulsion as a final step or at some earlier stage.

Sensitizing dyes useful in sensitizing the silver halide catalyst are described, for example, in U.S. Pat. 2,526,632 of 'Brooker et al. issued Oct. 24, 1950; U.S. Pat. 2,503,- 776 of Sprague issued Apr. 11, 1950; U.S. Pat. 2,493,748 of Brooker et al. issued Jan. 10, 1950 and U.S. Pat. 3,384,- 486 of Taber et al. issued May 21, 1968. Spectral sensitizers, which can be used, include the cyanines, merocyanines, complex (trinuclear ortetrauuclear) cyanines, holopolar cyanines, styryls, hemicyanines such as enamine, hemicyanines, oxonols and hemioxonols. Dyes of the cyanine classes can contain such basic nuclei as the thiazolines, oxazolines, pyrrolines, pyridines, oxazoles, thiazoles, selenazoles, and imidazoles. Such nuclei can contain alkyl, alkylene, hydroxyalkyl, sulfoalkyl, carboxyalkyl, aminoalkyl, and enamine groups that can be fused to carbocyclic or heterocyclic ring systems either unsubstituted or substituted with halogen, phenyl, alkyl, haloalkyl, cyano, or alkoxy groups. The dyes can be symmetrical or unsymmetrical and can contain alkyl, phenyl, e-namine or heterocyclic substituents on the methine or polymethine chain.

The merocyanine dyes can contain the basic nuclei described as Well as acid nuclei such as thiohydantoins, rhod anines, oxazolidenediones, thiazolidenediones, barbituric acids, thiazolineo-nes, and malononitrile. These acid nuclei can be substituted with alkyl, alkylene, phenyl, carboxyalkyl, sulfoalkyl, hydroxyalkyl, alkoxyalkyl, alkylamine groups or heterocyclic nuclei. Combinations of these dyes can be used if desired. In addition, supersensitizing addenda which do not absorb visible light may be included such as, for instance, ascorbic acid derivatives, azaindenes, cadmium salts, and organic sulfonic acid as described in U.S. Pat. 2,933,390 of McFall et al. issued Apr. 19, 1960 and U.S. Pat. 2,937,089 of Jones et al. issued May 17, 1960.

The sensitizing dyes and other addenda used in the practice of the invention can be added from water solutions or suitable organic solvent solutions can be used. The compounds can be added using various procedures including, for example, those described in U.S. Pat. 2,912,343 of Collins et al. issued Nov. 10, 1959; U.S. Pat. 3,342,605 of McCrossen et al. issued Sept. 19, 1967; U.S. Pat. 2,996,287 of Audran issued Aug. 15, 1961; and U.S. Pat. 3,425,835 of Johnson et al. issued Feb. 4, 1969.

A range of concentration of spectral sensitizing dye can be employed in the practice of the invention to provide spectral sensitivity. The desired concentration will -be influenced by the desired spectral sensitivity, other components in the system, the desired image, processing conditions and the like. Typically a concentration of the described spectral sensitizing dye is typically about 50 mg. to about 2 grams of spectral sensitizing dye per mole of catalyst, e.g., per mole of photosensitive silver halide.

While concentrations of the various components of the described element or composition can vary depending upon the desired image, the particular components, processing temperature and time and the like, the described element or composition can comprise about 0.10 to about 0.75 mole of the described reducing agent per mole of described oxidizing agent, about 0.005 to about 0.50 mole of the described catalyst per mole of described oxidizing agent, and about 50 mg. to about 2.0 grams of the described sensitizing dye per mole of described catalyst, e.g., per mole of photosensitive silver halide.

For example, a preferred photosensitive and thermosensitive composition or element can comprise photosensitive silver halide, an oxidizing agent, which comprises silver behenate.

(a) about 50 mg. to about 2.0 grams of 3-carboxymethyl- 5 [(3-methyl-2 3H -thiazolinylidene isopropylidene] rhodanine or 3-ethyl-5-[ (3-ethyl-2(3H)-benzothiazolylidene)isopropylidene]-2-thio 2,4 oxazolidenedione or l-carboxymethyl 5 [(3-ethyl-2(3H)-benzoxazolylidene)ethylidene]-3-phenyl 2 thiohydantoin per mole of silver halide,

(b) about 0.10 to about 0.75 mole of 2,2'-dihydroxy-1,l-

binaphthyl per mole of silver behenate oxidizing agent,

(c) about 0.005 to about 0.50 mole of photosensitive silver halide per mole of silver behenate oxidizing agent and (d) about 0.10 mole to about 1.05 moles of phthalimide activator-toning agent per mole of silver behenate.

An especially suitable photosensitive and thermosensitive element or composition, as described, comprises:

After exposure of the described photosensitive and thermosensitive element, the resulting latent image is developed merely by heating the element. Accordingly, another embodiment of the invention is: in a process of developing a latent image in an exposed photosensitive and thermosensitive element comprising a support,

(a) an oxidation-reduction image forming combination comprising (1) a reducing agent with (2) an oxidizing agent which comprises a heavy metal salt of an organic carboxylic acid, (b) a catalyst for the described image-forming combination, and (c) a sensitizing dye which comprises a merocyanine sensitizing dye having a rhodanine, thiohydantoin or 2- thio-2,4-oxazolidinedione nucleus, comprising heating the described element from about 80 C. to about 250 C.

A temperature range of about 125 C. to about 180 C. is usually suitable for developing and stabilizing a desired image. By increasing or decreasing the length of time of heating, a higher or lower temperature within the described range can be employed. A developed image is typically produced within a few seconds such as about 0.5 second to about 60 seconds.

The photographic process can comprise, for example, exposing to actinic radiation a photosensitive and thermosensitive element comprising a support,

(a) an oxidation-reduction image-forming combination comprising (1) silver behenate with (2) a bis-naphthol reducing agent as described, (b) photosensitive silver halide, (c) polyvinylbutyral (d) an activator-toning agent which comprises phthalimide, or succinimide, and (e) a blue speed increasing merocyanine dye, as described, comprising heating the above described element to about C. to about 250 C. for about 0.5 second to about 60 seconds.

A preferred process of developing and stabilizing a latent image in an exposed photosensitive and thermosensitive element comprising a support,

(a) an oxidation-reduction image-forming combination comprising (1) 2,2'-dihydroxy-1,1'-binaphthyl and 2) silver behenate,

(b) photosensitive silver halide,

(c) a sensitizing dye comprising 3-carboxymethyl-5-[(3- methyl 2 (3H) thiazolinylidene)isopropylidene]- rhodanine,

(d) an activator-toning agent comprising phthalimide,

(e) an image amplifier comprising zinc acetate,

(f) a photographic speed increasing onium halide comprising l-phenethyl-Z-picolinium bromide or trimethylphenylammonium bromide,

(g) a binder comprising polyvinylbutyral, and

(h) a stabilizer precursor comprising 5-acetyl-4-methyl-2- (3-oxobutylthio)thiazole,

comprising heating said element at about 80 C. to about 250 C. for about 0.5 second to about 60 seconds.

Processing is usually carried out under ambient conditions of pressure and humidity. Pressures and humidity outside normal atmospheric conditions can be employed if desired; however, normal atmospheric conditions are preferred.

Any suitable means can be used for providing the desired processing temperature range. The heating means can be a simple hot plate, iron, roller, or the like.

In some cases, if desired, an element can be prepared wherein the described silver halide can be in one layer and other components in other layers. For example, an element according to the invention can comprise a support, a layer containing photographic silver halide and a blue speed increasing sensitizing dye, and a layer comprising a so-called processing composition comprising (a) a silver salt of an organic acid, (b) a reducing agent, as described, and (c) an activator-toning agent, as described The processing composition and/ or the silver halide layer can contain other addenda, as described, also. The processing composition can contain the sensitizing dye.

A typical processing composition is a processing composition comprising (a) silver behenate, (b) 2,2-dihydroxy-1,1'-binaphthyl, and (c) phthalimide.

Typically, a polyvinylbutyral binder is employed with this processing composition.

Other addenda known to be useful in photosensitive and thermosensitive elements of this type, such as de scribed in British Pat. 1,161,777 published Aug. 20, 1969, US. Pat. 3,152904 of Sorensen and Shepard issued Oct. 13, 1964 and US. Pat. 3,457,075 of Morgan and Shely 13 patented July 22, 1969 can be employed in the practice of the invention.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 This is a comparative example.

A photographic, non-spectrally sensitized control element is prepared as follows:

A coating composition is prepared by mixing the following components:

Silver behenate g 42.0 Behenic acid g 32.0 Polyvinylbutyral g 15.0 Phthalimide g 8.5 Acetone-toluene (1:1 parts by volume) ml 500 aMl.

Acetone containing 6.3% by weight 2,2"dihydroxy- 1,1'-binaphthyl 26.2 Acetone-toluene (1:1 parts by volume) 27.8

The resulting final dispersion is coated on a resin coated paper support at a wet thickness of 6.0 g. of dispersion per square foot of support, dried, and sensitometrically exposed for seconds to tungsten light which has been filtered by a combination of a Wratten 38A and a Wratten 35 filter. This provides exposure of the element to light in the blue region of the spectrum. The element is then processed by heating on a curved hot block for 10 seconds at a temperature of 140 C. The resulting jetblack image is assigned a blue speed, i.e., a relative speed in the range of 100.

EXAMPLES 2-7 These examples illustrate the invention.

The procedure set out in Example 1 is repeated with exception that 3.5 ml. of an acetone solution containing 0.01% by weight of the following individual dyes is added to the final coating composition after the addition of the 2,2-dihydroxy-1,1'-binaphthyl reducing agent.

dene)isopropylidenekhodanine.

The coated element is exposed and processed as in Example 1. Table I contains the Example number, Dye number and the blue speed relative to Example 1, the control coating. The relative blue speed listed in Table I demonstrates that merocyanine dyes, containing a rhodanine or thiohydantoin nucleus, increase the intrinsic blue speed of the element as described in the invention.

TABLE 1 Example Relative Dye number blue speed number None, control EXAMPLES 55-15 These are comparative examples with preferred blue speed increasing, merocyanine, sensitizing dyes, i.e., dyes I and VI.

Several photosensitive and thermosensitive elements are prepared as follows:

A dispersion is prepared by mixing the following components:

Ml. Silver bromide-silver behenate dispersion (described in Example 1) 2.0 Acetone containing 3.0% by weight of 2,2'-dihydroxy-1,1'-binaphthyl 2.0 Acetone containing 0.01% by weight of the individual dyes listed below 0.25 Acetone-toluene (1:1) 3.00

Each final dispersion is coated on a suitable paper support at a wet thickness of about 0.004 inch, dried, exposed for 0.5 second to tungsten light, filtered through the same Wratten filter combination as described in Example 1, and processed by heating on a curved hot block for 8 seconds at 135 C.

Example number Dye No. Dye

10 VII-.-" 3,3-diethyl-9-methylthiacarboeyanine bromide.

11 VIII 1,1-diethyl-2,2-cyarnne iodide.

12 IX 5chloro-3-ethoxyearbonylmethyl-B-methyl-Q- phenyl4,5-benzothiacarbocyarfine bromide.

13 X 5-[(3-ethyl-2(3H)-naphtho-[2,1]-0xazolylidene) ethylidene]-3-n-hepty1-1-phenyl-2-thiohydantoin.

14 XI 3-ethyl-5-[(3-ethyl-2(3H)-napl1th0-[2,1]-

oxazolylidene)ethylidene]-1-phenyl-2-thio hydantoin.

15 XII..." Anhydro-3-ethyl-9-methyl-3-(4-sulfobutyl)4,5-

benzothiacarboeyanine hydroxide.

Table II lists the Example number, Dye number and blue speed relative to Example number 8, a control coating which contains no dye.

The results in Table II demonstrate that the preferred dye, i.e., Dye VI increases the blue speed of the element, as described, to a surprising degree (+2.10 log E). The results also demonstrate that some dyes do not cause increase in blue speed and some dyes decrease blue speed or can cause desensitization (Example 14).

EXAMPLE 16 This example demonstrates that the preferred dye, i.e., Dye VI, enhances the rate of dry physical development of the photosensitive element in comparison to an element that does not contain the preferred dye.

Samples of each of the elements as prepared in Example 1 and Example 9 are exposed for 60 seconds through a step wedge to white light which has been filtered by a Wratten 35 and a Wratten 38A filter providing an exposure in the wavelength range of 320 to 470 millimicrons with a maximum of 420 millimicrons. The exposed samples are heat processed at various time intervals on a curved hot block at a temperature of C. Table III lists the coating format, sensitometric data and exposure times relative to this example.

TABLE III Time of heat development (sec.) at

140 C- Dmin. mux.

The sensitometric results listed in Table III demonstrate that the coating containing Dyee VI attains a maximum density of 1.32, e.g., in 6 seconds, whereas the control coating requires 8 seconds to attain the same maximum density. Also, at eight seconds the element containing Dye VI attains a maximum density of 1.60 whereas the element containing no dye does not attain this maximum density even after 10 seconds.

EXAMPLE 17 This illustrates the invention.

A 20% increase in maximum density is realized upon addition of 2.5 ml. of a methanol solution containing 1.0% by weight of a divalent metal salt image amplifier which is zinc acetate to the final dispersion of Example 9 before coating on a support.

EXAMPLE 18 This illustrates the invention.

The amount of print-out due to room light handling of a processed element is reduced 50% by the addition of 25 milliliters of an acetone solution containing 0.8% by weight of an image stabilizer precursor which is acetyl-4-methyl-2-(3-oxobutylthio)thiazole to the final dispersion of Example 9 before coating on a support.

EXAMPLE 19 This illustrates the invention.

Additional photosensitivity, i.e., an increase of about 0.10 to about 0.15 log E, is conferred upon the element as described in Example 9 upon addition of a speed increasing onium halide compound which is trimethylphenylammonium bromide, at a concentration of about 0.024 mole/mole AgBr, to the final dispersion of Example 9 before coating on a support.

EXAMPLE 20 This illustrates the invention. A dispersion is prepared by ball milling the following components together for about 18 hours:

Silver behenate g 42.0 Behenic acid g 32.0 Polyvinyl butyral g 15.0 Phthalimide g 8.5 Sodium bromide g 2.4 Acetone-toluene( 1 :1 parts by volume) ml 500.

A 141.0 ml. aliquot of the resulting dispersion is then combined with the following components:

Acetone containing 6.3% by weight 2,2'-dihydroxy- 1,1-binaphthyl 52.5 Acetone-toluene(1:l parts by volume) 56.5

Each element is exposed to white light for 0.5 second and then contacted with a heat metal block at C. for ten seconds.

The control element is assigned a relative photographic speed of 100. Compared to the control, the element containing Dye XIII provides a relative photographic speed of 1620.

EXAMPLE 21 The procedure set out in Example 20 is repeated with the exception that 4.4 ml. of an acetone solution containing 0.01% by weight of Dye VI, as described in Ex ample 9, is employed in place of Dye XIII. The resulting element provides a relative photographic speed of 2690 compared to the control set out in Example 20.

This demonstrates that of preferred Dyes XIII and VI that Dye VI provides surprisingly higher relative speed.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is:

1. A photothermographic thermosensitive and thermosensitive element comprising a support having thereon (a) an oxidation-reduction image-forming combination comprising (1) 2,2-dihydroxy-1,l'-binaphthyl and (2) silver behenate,

(b) photosensitive silver halide,

(c) a sensitizing dye comprising 3-carboxymethyl-5- [(3 methyl 2 (3H)-thiazolinylidene)isopropylidene] rhodanine,

(d) an activator-toning agent comprising phthalimide,

and

(e) a binder comprising polyvinylbutyral.

2. A photothermographic thermosensitive and thermosensitive composition comprising (a) an oxidation-reduction image-forming combination comprising (1) 2,2-dihydroxy-1,1-binaphthyl and (2) silver behenate,

(b) photosensitive silver halide,

(c) a sensitizing dye comprising 3-carboxymethyl-5- [(3-methyl 2(3H) thiazolinylidene)isopropylidene]- rhodanine,

(d) an activator-toning agent comprising phthalimide,

and

(e) a binder comprising polyvinylbutyral.

3. A photothermographic element comprising a support having thereon (a) an oxidation-reduction image-forming combination comprising (1) a phenolic reducing agent, and (2) an oxidizing agent which comprises a silver salt of an organic carboxylic acid,

(b) photosensitive silver halide,

(c) an activator-toning agent, and

(d) a sensitizing dye comprising 3-carboxymethyl-5- [(3 methyl 2 (3H)-thiazolinylidene)isopropylidene]-rhodanine.

4. A photothermographic element comprising a support having thereon (a) an oxidation-reduction image-forming combination comprising (1) a bis-beta naphthol reducing agent, and (2) an oxidizing agent which comprises a silver salt of an organic carboxylic acid,

(b) photosensitive silver halide,

(c) an activator-toning agent comprising succinimide,

phthalazinone or phthalimide, and

(d) a sensitizing dye comprising 3-carboxymethyl-5- [(3 methyl 2 (3H) thiazolinylidene)isopropylidene]-rhodanine.

1 7 5. A process of developing and stabilizing a latent image in an exposed photothermographic element comprising a support having thereon (a) an oxidation-reduction image-forming combination comprising 1) 2,2'-dihydroxy-1,1'-binaphthyl and (2) silver behenate,

(b) photosensitive silver halide,

(c) a sensitizing dye comprising 3-carboxymethyl-5- [(3 methyl 2(3H) thiazolinylidene)isopropylidene]-rhodanine,

(d) an activator-toning agent comprising phthalimide,

(e) a binder comprising polyvinyl-butyral, and

(f) a stabilizer precursor comprising 5-acetyl-4-methyl- 2-(3-oxobutylthio) thiazole, comprising heating said element at about 80 C. to about 250 C. for about 0.5 second to about 60 seconds.

References Cited UNITED STATES PATENTS Sorensen 9663 Kendall 96140 Stevens 96140 Hunt 96140 Grant 117-368 Grant 11736.8 Morgan 9667 Blake 9694 NORMAN G. TORCHIN, Primary Examiner M. F. KELLEY, Assistant Examiner US. Cl. X.R.

96140, 48 QP UXR, 66T UXR, 95 UXR 75g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION new No. 3,761,279 Dated September 25, 1973 Inventor(s) Richard A. deMauriac and Wilbur S. Gaugh It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

7 Column 3, lines 51-52, that part of the formula reading "benzoxazolyidene" should read ---benzoXazolylidene---.

. column 5, line 15, "bis-naphthols" should read --bisnaphthol--.

13, line 52, that part of" the formula reading "carboxyethy. should read ---carboXyethyl-- Column 1M, line 29, that part of the formula reading 5 chloro should read ---5' -chloro---.

Column 15, line 15, "Dyes should read ---Dye-'--'.

In the Claims:

Column 16, lines 2 L-25, "thermosensitive and thermosensitive" should be deleted.

Columnl6, lines 38-39,"'thermosensitive and thermosensi'tive" should be deleted.

Signed and sealed this 20th day of August 1974.

(SEAL) Attest:

I MCCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

